The Montreal Protocol for the protection of the ozone layer, signed in October 1987, mandates the phase out of the use of chlorofluorocarbons (CFCs). Materials more “friendly” to the ozone layer, such as hydrofluorocarbons (HFCs) eg HFC-134a replaced chlorofluorocarbons. The latter compounds have proven to be green house gases, causing global warming and were regulated by the Kyoto Protocol on Climate Change. The emerging replacement materials, hydrofluoropropenes, were shown to be environmentally acceptable i.e. have zero ozone depletion potential (ODP) and acceptable, low GWP. The present invention is directed towards a process for manufacturing of hydrofluoroolefins such as hydrofluoropropenes and/or hydrochlorofluoroolefins. The process of the present invention is based on a two-step reaction process including a gas or liquid phase, fluorination followed by a catalytic gas phase fluorination to produce the desirable fluoroolefins.
Methods of preparing hydrofluoroalkenes are known. For example, WO2007/079431 discloses processes for the production of fluorinated olefins, including hydrofluoropropenes. The processes which are broadly described as a single reaction or two or more reactions involve fluorination of compounds of the formula C(X)mCCl(Y)nC(X)m to at least one compound of formula CF3CF═CHZ, where each X, Y and Z is independently H, F, Cl, I or Br and each m is independently 1, 2 or 3 and n is 0 or 1. The examples and preferred embodiments disclose multi-step processes such a reaction sequence wherein a feedstock of 1,1,2,3 tetrachloropropene (1230xa) is fluorinated in a catalyzed, gas phase reaction to form a compound such as 2-chloro-3,3,3-tri-fluoropropene (HCFO-1233xf). The 2-chloro 3,3,3-tri-fluoropropene is then converted to 2-chloro-2,3,3,3-tetrafluoropropane (HCFC-244bb) via a liquid phase, catalyzed reaction. Followed by dehydrochlorination of the 2-chloro-2,3,3,3-tetrafluoropropane (HCFC-244bb) to 2,3,3,3-tetrafluoropropene (HFO-1234yf) via a catalyzed, gas phase reaction.